The invention relates to a system for the optical display and the photoelectric scanning of the contents of a counter equipped with counting wheels.
A system of this type is known (GB-A No. 2,018,069) in which, for the display of the contents of an electric counter equipped with counting wheels, optical markings consisting in each case of four individual lines, are assigned to the numerals in question of the counting wheels. Different respective line thicknesses make possible the selection of a certain code. The scanning of the reflecting line pattern takes place by means of a light pen, which is guided along the row of the individual lines, which is the reason why the four individual lines of each individual marking have to be arranged sequentially in the same scanning direction. This type of marking requires a relatively large total surface, so that on the outer surface or periphery of the counting wheel, only a small free area remains for the visually readable nunbers; the visual reading of the contents of the counter is consequently made considerably more difficult. The markings which catch the eye also disturb the esthetic effect of the counter.
It is also known (EP-A No. 0,060,937) to use diffraction-optical elements, such as, for example, holograms or diffraction gratings, as markings, which are impressed onto a thin transparent sheeting and cover the numerals of the counting wheels, so that the numerals are visible through the holograms or diffraction grating. However, the reading of the contents of the counter represented by such diffraction-optical elements, makes it necessary that the light transmitter and the light receiver are arranged at a predetermined spatial angle, and consequently cannot be carried out easily by means of a manually guided light pen.
From U.S. Pat. No. 4,085,314 it is also known to produce coded markings from reflecting material, which, for example, serve for the characterization of groceries.
German Pat. No. 6 80 34 441.8 relates to a counter, including a reading arrangement, but where the coding requires a space separate from that of the numerals on the counting wheels.
British patent specification No. 815,124 relates to improvements in counter mechanisms with movable indicating fields, each bearing a visually readable symbol, and a coded representation of a symbol adapted to yield a distinctive electrical response when the field or an image thereof is scanned by electrical scanning means. The visually readable symbol and the coded representations are at least partially superimposed on each other, while the visually readable symbol is in a form which does not yield such a response. The counter mechanism requires, however, light sensitive means adapted to respond to the coded representation only of the illuminated field, and means controlled directly or indirectly by the light sensitive means for generating one or more electrical signals in accordance with the coded representation. The color of the light provided by the illuminating means, and the spectral density of the light sensitive means have been so chosen in relation to colors of the coded representations, the visually readable symbols, and the background of the indicating fields, that only the coded representations are distinguished by the light sensitive means.
Swiss Pat. No. 586,431 relates to a method for determining information on an information carrier, wherein a portion consists of a design in the form of perforations representing, in turn, a pattern corresponding to alphanumeric symbols; this patent does not relate to any counters as such.